The present invention relates to a magnetoresistive head and a manufacturing method thereof.
FIG. 2 is a cross sectional view of a sensor portion of a magnetoresistive head in described in Japanese Patent Laid-Open No. 2002-151755 as viewed from an air bearing surface. At first, as shown in FIG. 2, a multi-layered film L is formed with a free layer 2, a non-magnetic layer 3, a pinned layer 4, an anti-ferromagnetic layer 5, and a cap layer 6 on an underlayer 1.
Further, a protruded portion 8a is formed at the central area of a lower dielectric gap layer 8, and extended portion 8b extending in the direction of the track width is formed from both lateral end faces of the protruded portion 8a in the direction of the track width. The multi-layered film L is stacked on the protruded portion 8a. 
Further, a magnetic domain control underlayer 9 made of Cr is formed from a portion on the extended portion 8b to both end faces of the multi-layered film L in the lateral direction of the track width. Further, a magnetic domain control film 10 is formed on the magnetic domain control underlayer 9. The magnetic domain control underlayer 9 is used for improving the magnetic characteristics (coercive force or the like) of the magnetic domain control film 10. Then, an electrode film 11 is formed on the magnetic domain control film 10.
In this case, magnetization of the free layer 2 is aligned in the direction of the track width and the magnetic domain of the free layer 2 is controlled by a bias magnetic field from the magnetic domain control film 10.
FIG. 3(a) is a view schematically showing magnetic charges, bias magnetic field HbL, anti-magnetic field Hd of free layer 2, and exchange interaction Jex in the sensor portion of an existing magnetoresistive head.
In the existing structure shown in FIG. 3(a), magnetic charges are generated on both right and left end of the free layer, to form anti-magnetic field Hd in the direction opposite to the magnetizing direction of the free layer in the inside of the free layer. This makes the control of the magnetic domain difficult. In order to obtain favorable reading characteristics with less head noise, it is necessary to provide a sufficient bias magnetic field HbL from the magnetic domain control film 10 to the free layer 2 thereby controlling the magnetic domain of the free layer 2.
However, when a sufficient bias magnetic field HbL is applied to the free layer 2, low sensitivity regions (dead zones) are formed on both right and left ends of the free layer 2 and lower the read output of the head. Further, to avoid the generation of the anti-magnetic field Hd, it is possible to remove the magnetic domain control underlayer 9 to provide direct contact of the magnetic domain control film 10 with the free layer 2. However, since the coercive force of the magnetic domain control film 10 is decreased, the magnetic domain of the free layer 2 cannot be controlled properly.
The present invention intends to solve the foregoing problems and provide a magnetoresistive head capable of properly controlling the magnetic domain of the free layer and a manufacturing method thereof.